What critical means of transport did the Soyuz exclusively provide for international crews after the 2011 retirement of which vehicle?

The only reliable means for any crew—American, European, Japanese, or Russian—to reach the ISS and return safely following the retirement of the American Space Shuttle fleet in 2011

Following the retirement of the American Space Shuttle fleet in 2011, the geopolitical and operational landscape shifted such that the Russian Soyuz became the singular, reliable method for maintaining a continuous human presence aboard the International Space Station. This dependency meant that American, European, and Japanese astronauts and cosmonauts relied solely on Soyuz hardware for transit to and from the orbiting laboratory for nearly a decade. This period underscored the intense reliance placed on the proven reliability built up over thousands of Soyuz flights across the international community.